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Philadelphia, PA (SportsNetwork.com) - Roster turnover is an unavoidable part of college basketball.

Players come and players go and, in the modern era, they often go fairly soon after arriving on campus.

In last Thursday's NBA Draft, the first four picks were all freshmen, the first time that has happened since the modern draft lottery rules were put in place in 1994.

Of the other 56 picks made, 41 came from the college ranks. Add to those the players who graduated and underclassmen who declared and went undrafted, and that leaves a pretty large group of contributors who need to be replaced next season.

Finding permanent substitutes for some will be easy, but there are some former players who will be extremely difficult, if not impossible, to replace this season.

Perhaps the most difficult job in this area belongs to Creighton coach Greg McDermott, who must replace not only the best player on his team but his own son.

Doug McDermott, the 6-foot-8 forward affectionately known as "Dougie McBuckets," is a rarity in the modern college game, as he stayed for all four seasons with the Bluejays before heading off to the professional level.

In that time, he smashed a number of Creighton scoring records, while ranking among the top five players in the country in scoring his sophomore, junior and senior seasons. He saved his best for last, leading the nation in points per game (26.7) in his final campaign while shooting 52.6 percent from the floor and 44.9 percent from 3-point range. He also was featured on the cover of Sports Illustrated in a homage to Larry Bird, as he became one of the most recognizable names in the sport.

McDermott's versatile scoring, whether it be by contested jumper or step-back fadeaway, put Creighton on the map and cemented it as one of the premier programs in the new Big East.

To stay there, Greg McDermott will need to drain every last bit of talent and production out of a roster that no longer features his high- scoring son. That is quite a challenge as the Bluejays also lost second- leading scorer Ethan Wragge (10.4 ppg) among others. Austin Chatman (8.1 ppg, 4.4 assists per game) will be the best returning offensive threat, but the 6- foot guard has never shown or needed to show the type of scoring flare that is now missing for the Bluejays.

Speaking of replacing a potent scorer, both Louisville and North Carolina State will have their hands full attempting to find a top offensive option this offseason.

The ever talented and confident Russ Smith (18.2 ppg) won't be running the floor for the Cardinals, which leaves a gaping hole for a team that had some solid scorers, but none who could create like Smith. Montrezl Harrell (14 ppg, 8.4 rebounds per game) is the top returning choice, but he is a one- dimensional threat, relying too much on shots close to the basket.

N.C. State lost even more offensive firepower than Louisville when T.J. Warren decided to move on to the NBA after two years in Raleigh. Warren (24.9 ppg) was the ACC's leading scorer and the conference's player of the year for the 2013-14 season, making him the first player from N.C. State since Julius Hodge to earn the honor.

Finding a new top option will be extremely difficult. Warren accounted for just over 35 percent of the Wolfpack's scoring output and leaves a team that had just three other players who netted more than five points per game.

Top scorers on some other squads also have moved on with Marcus Smart shipping off to the Boston Celtics from Oklahoma State and Spencer Dinwiddie trading in his Colorado jersey for one from the Detroit Pistons.

However, both Smart and Dinwiddie provided much more than scoring for their respective squads.

Dinwiddie, a 6-6 guard, who often ran the point for the Buffaloes, was easily the most-important player on the floor every game. He led Colorado in scoring (14.7 ppg), assists (3.8 apg) and steals (1.5 spg) and helped them to a 14-3 record to start the 2013-14 campaign. However, in mid-January he tore his ACL and the Buffaloes got a look at how they would fare without their star guard.

The results were not pretty. The Buffaloes went just 9-9 down the stretch and limped into the NCAA Tournament, where they were blasted by Pittsburgh, 77-48. Hopefully, they can find some answers in the offseason or face an even worse fate in 2015.

Smart also gave Oklahoma State a preview of life without him this past season. After an altercation with a fan during a 65-61 loss to Texas Tech in early February, the 6-4 guard was tagged with a three-game suspension. The Cowboys lost all three of those games, part of a seven-game losing streak which nearly pushed them out of NCAA Tournament contention. Fortunately, Smart's return facilitated a four-game winning streak that likely saved the season.

Like Dinwiddie, Smart provided more than just the best scoring average (18 ppg) on his team. He also grabbed 2.9 steals per game, the third-best mark in the nation. On top of that, his tenacity and will to win were second to none.

Willing his team to victory was the habit of another player, who will be sorely missed next season. National champion Connecticut may have locked up head coach Kevin Ollie to a five-year extension, but without Shabazz Napier, adding another title will prove to be an improbable task.

Napier, who was named American Athletic Conference Player of the Year, did just about everything for the Huskies, leading the team in scoring (18 ppg), rebounds (5.8 rpg), assists (4.9 apg) and steals (1.8 spg), while hitting big shot after big shot all season en route to the Huskies' fourth NCAA crown.

This selection of departing players only scratches the surface of the talent that has moved on from the college game. However, while turnover is always guaranteed, so is the fact there will be new and exciting talent to look forward to next season.